Various types of vertical hydraulic press for forming ceramic tiles are known, which exhibit a structure or frame, which connects the mobile and fixed parts to one another, which has to be particularly rigid and, in the example, takes on the typical closed frame shape, normally with two uprights with accessibility to the work plane from two opposite sides. Commonly these ceramic tile-forming presses exhibit a free space between the two uprights or columns (which defines the inlet mouth of the material to be formed) that is very large, indeed as large as possible. This space is in fact dimensioned on the basis of the largest dimension of the pressing rectangle which represents the flat surface on which the pressing action will be performed, necessarily discontinuously and intermittently.
This fact, of having a large introduction space to which a decidedly smaller depth usually corresponds, is largely induced by the need to render the run of the usual loading carriage of the powder material as small as possible, essentially with the aim of not overly penalizing the rhythm of production. Consequently to the considerable space between the two uprights or columns, in the known realizations of oldest date the resistant structure of the press develops in the perpendicular plane to the inlet direction of the material to be formed. This structure is therefore rather large and tall—so tall as to require, in some cases, a partial interment having the aim of giving the structure the required stability.
The height of these structures is substantially due to the usual constructional technique which comprises use of a base and an upper crossbar, connected by the uprights or columns, which must be of considerable thickness—in the vertical direction—in order to guarantee the two planes supporting the reactions deriving from the application of the pressing force an accentuated undeformability: these are in fact the planes on which the lower and upper parts of the die act.
By way of example, in hydraulic presses used for forming ceramic tiles able to exert a pressing force of 7000 tonnes and with a free space between the uprights or columns of greater than 2 meters, the structure can reach heights of greater than 7 meters, of which about a third is interred.
In consideration of the forces in play, in order to guarantee these known structures those characteristics of deformability which enable them to be adapted in part to any loading defects in the powders to be pressed, various technical solutions have been adopted, including some which are constructionally complex but which are nevertheless not fully satisfactory.
In particular the present applicant has provided interesting technical solutions which are the objects of publications EP 1118456 and EP 1441899. These solutions, which are able to provide good responses to the main above-cited problems in the prior art, exhibit a modular structure composed by a plurality of resistant elements that are assemblable in series, one consecutively to another with an arrangement and a modular organisation with which the variation in the number of the resistant elements 1 assembled enables a proportional variation in the maximum pressing force that can be borne.
Us publication U.S. Pat. No. 3,563,167 discloses a frame of a press composed of a certain number of flat sub-frames, each of which defines an opening. The sub-frames are interconnected by means of plates and maintained distanced from one another.
For all of these realizations it is important and determinant to comprise resistant elements in the form of ring-closed arches which must guarantee the necessary resistance for a high number of cycles without any structural yielding or the beginnings of such occurring.
The present invention is directed principally to a considerable improvement of the characteristics or resistance to fatigue of the known applications. With this, the invention is aimed at guaranteeing a working life of the resistant elements of the presses that is in line with the working life expected for the plants in which the presses themselves are inserted.
Further, some of the realizations actuated in conformity with the inventions of the cited publications are characterised by a relatively complicated construction, mainly caused by the components to be assembled.
The main aim of the present invention is to obviate the limitations in the prior art, by disclosing a compact, light and simple press in terms of constitution and assembly, which is structured in line with a modular concept.
An advantage of the invention consists in the fact of presenting a structure which, given an equal maximum-applicable compression force, is characterised by considerable lightness and a very contained overall size.
A further advantage of the invention consists in being constructionally very simple in general, in particular as far as the structure of the resistant elements or arches are concerned, as well as in relation to the number of components and the assembly mode thereof.
These aims and advantages and others besides are all realised by the present invention, as it is characterised by the claims as set out herein below.